On Wed, Jan 31, 2018 at 12:58:56PM +0100, Daniel Borkmann wrote:
> syzkaller was able to generate the following XDP program ...
>
> (18) r0 = 0x0
> (61) r5 = *(u32 *)(r1 +12)
> (04) (u32) r0 += (u32) 0
> (95) exit
>
> ... and trigger a NULL pointer dereference in ___bpf_prog_run()
> via bpf_prog_test_run_xdp() where this was attempted to run.
>
> Reason is that recent xdp_rxq_info addition to XDP programs
> updated all drivers, but not bpf_prog_test_run_xdp(), where
> xdp_buff is set up. Thus when context rewriter does the deref
> on the netdev it's NULL at runtime. Fix it by using xdp_rxq
> from loopback dev. __netif_get_rx_queue() helper can also be
> reused in various other locations later on.
>
> Fixes: 02dd3291b2f0 ("bpf: finally expose xdp_rxq_info to XDP bpf-programs")
> Reported-by: syzbot+1eb094057b338eb1f...@syzkaller.appspotmail.com
> Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
> Cc: Jesper Dangaard Brouer <bro...@redhat.com>
> ---
> v1 -> v2:
> - Rename netif_get_rx_queue() into __netif_get_rx_queue().
>
> [ Note: Needs to wait till Linus pulled Dave's net-next so
> the affected commit lands in bpf tree. ]
Applied to bpf tree, Thank you Daniel.
